This application claims the priority of German Patent Application No. 101 31 284.9 filed Jun. 28, 2001, which is incorporated herein by reference.
The invention relates to an apparatus for converting measurement signals into digital signals that are suitable for processing in a microprocessor. More particularly the present invention relates to such an apparatus wherein the signals have been initiated in a piezo sensor by accelerations acting on the sensor during the impacts of a percussion device, particularly a hydraulic hammer, and are used to determine the number of work strokes that have been executed in the impact direction of the percussion device.
Similarly to the solution known from the document DE 199 23 680 A1, the invention is based on the realization that the current total number of impacts executed by the percussion aggregate represents a relevant variable for determining the active service life, andxe2x80x94through a comparison to comparable preset valuesxe2x80x94can also yield information regarding the state of utilization of the relevant percussion aggregate.
The simplest method of obtaining information about the state of utilization of the percussion device is to check whether the current total number of impacts executed by the percussion device has attained an order of magnitude that corresponds to the total number of impacts that defines a maintenance-free operating period.
The above cited document, which was published prior to this application, proposes to determine the service life and the state of utilization of a hydraulic percussion device by generating measurement signals during the individual, consecutive operating periods of the percussion device, from which the number of strokes that the percussion piston of the percussion device has executed in a direction of movement can be determined. The publication further proposes to continuously add the number of signals and store the total number, and make the current total number of signals recognizable, at least temporarily, in the form of an indicator of the state of utilization.
To generate the measurement signals that indicate the number of impacts, a measurement-value indicator can be provided in the form of a piezo sensor, which detects oscillations that have been initiated by the percussion-piston strokes.
It is the object of the invention to provide an apparatus for converting relevant measurement signals that have been generated by a piezo sensor into digital signals, with the apparatus reliably supplying the necessary information and having a low energy requirement, despite the difficult working conditions expected in the use of hydraulic percussion devices.
Furthermore, the novel conversion apparatus is intended to be embodied to permit a compact design, and thus easily be mounted, without any special measures, to the percussion device at a location that is suitable for generating measurement signals.
Finally, the conversion apparatus is intended to be distinguished by the fact that it is extensively independent of the design, structural size and other characteristic features of the percussion device to be monitored.
The above object generally is accomplished by a novel conversion apparatus wherein the underlying concept lies in re-forming measurement signals, which have been generated in consecutive stages by a piezo sensor, into digital signals that provide sufficiently reliable information about the impacts executed by the percussion device, and are in a suitable form for processing in a microprocessor.
The conversion apparatus according to the invention includes: a rectifier that is connected to the output of the piezo sensor and suppresses the negative component of the measurement signal produced by the piezo sensor; a peak-value detector, that is connected to the output of the rectifier and converts the remaining, positive component of the measurement signal into an envelope curve; a high-pass filter that causes the envelope curves of consecutive measurement signals to be converted into intermediate signals whose amplitude has a regenerative zero passage; and a comparator, which is disposed downstream of the high-pass filter and is connected on the output side to the digital input of the microprocessor, that effects the conversion of the intermediate signals into digital signals having a rectangular amplitude response.
The high-pass filter changes the signals that are introduced into it such that their amplitude has a perfect zero passage. Accordingly, the conversion apparatus is automatically adapted to the associated percussion device. Consequently, the conversion apparatus can be used in connection with differently-configured percussion devices without necessitating an equipment conversion.
Within the scope of the invention, a piezoelectric shock sensor, such as is found in a laptop for protecting the hard disk, can be used as a piezo sensor.
According to a feature of the invention, the comparator additionally has a capacitor that is designed such that only digital signals located at a predetermined minimum interval from the digital signal of the preceding impact are present at the comparator output. The additional capacitor therefore assures the suppression of xe2x80x9cerror signalsxe2x80x9d also generated by the piezo sensor, which may be initiated, for example, by accelerations of the percussion aggregate that are not typically anticipated.
The invention is preferably embodied such that the piezo sensor simultaneously forms the energy source for the components disposed upstream of the comparatorxe2x80x94namely, the rectifier, the peak-value detector and the high-pass filterxe2x80x94and the comparator is connected to an energy supply that is independent of the piezo sensor. The advantage of this feature is that the conversion apparatus, with the exception of the comparator, requires no external energy supply, and only exhibits a low energy consumption.
Accordingly, it is possible to equip the conversion apparatus and the downstream microprocessor with an integrated battery unit that may permit a service life of more than five years. The battery unit can particularly comprise one or more lithium-thionyl-chloride batteries.
In a measure for improving the handling and the economical aspect of the conversion apparatus, the piezo sensor, the rectifier, the peak-value detector, the high-pass filter and the comparator can be combined with the microprocessor to form a combined mechanical component, which is secured as a unit to the housing of the percussion device.
The listed components, as well as the aforementioned battery unit and the capacitor that may additionally be associated with the comparator, are preferably secured inside a metallic sleeve by an elastic filling compound, while the sleeve is secured to the housing of the percussion device by an elastic damping layer. The oscillating behavior of the filling compound and the damping layer stipulates that they be designed such that the accelerations originating from the percussion device initiate the necessary signals in the piezo sensor with sufficient reliability.
In a normal scenario, it suffices for the piezo sensor, the rectifier, the peak-value detector, the high-pass filter and the comparator to be designed, and matched to one another, such that the components are capable of functioning at percussion-device impact frequencies between 3 and 70 Hz. This embodiment renders the conversion apparatus extensively independent of the design, structural size and other characteristic features of the percussion device, without significant adaptive measures.
The invention is described in detail below in conjunction with the drawing.